It was, in many respects, the most brutal assault so far: a two-year-old child killed instantly by a single blow to the skull; her critically injured parents rendered senseless by multiple head traumas. Clotted gore soaked the bed where they all lay. Across the walls and curtains around them, blood spatters radiated like birdshot. And yet, despite this evidence of what must have been a savage frenzy of violence, no one in the neighborhood had heard a thing. The perpetrator had been able to escape without a single witness to the crime, and with hours to spare before his deed was detected. The axman was apparently becoming even more adept at his trade with time. The crime had been discovered at about seven o''clock on a Sunday morning. Several neighbors had made earlier visits to the grocery, which usually opened at five a.

m., and had merely walked away when they found it closed. But one little girl named Hazel Johnson was more persistent. After getting no response at the front door, she decided to try around back. In the alley leading to the rear of the building, she found a chair set up below a side window. She climbed up on the chair and peered inside, but couldn''t see anything in the murky morning light. So she continued down the alley to the backyard. There she found the back door closed, but with one of its lower panels missing.

Puzzled, she called a passerby into the yard, and he persuaded her to go inside, perhaps because she was small enough to fit through the missing panel. She crawled in--and moments later burst out the back door, screaming. Aroused by this clamor, a young neighbor named Frank Jordano ran over with his aging father, Iorlando. They found Charles Cortimiglia half-conscious on the floor, and Rose Cortimiglia clutching her lifeless toddler and sobbing inarticulately. Her husband, Charles, roused out of his stupor by the younger Jordano, sat up on the floor. "Frank," he said. "I''m dying. Go for my brother-in-law.

" It was the last thing he would say for several days. Since the town of Gretna was in Lafayette Parish, Peter Leson, chief of the Gretna police, and Lafayette sheriff Louis Marrero would conduct the investigation of the Cortimiglia case, with Superintendent Mooney''s force merely assisting from afar. What Leson and Marrero found at the scene, however, indicated that the crime was clearly related to the previous year''s cases across the river. The axman''s signature modus operandi was obvious--from chiseled door panel to rummaged belongings, with little sign of anything of value actually being taken. This time, a box containing money and jewelry was found undisturbed in the bedroom, along with $129 in cash hidden under the Cortimiglias'' mattress. But two trunks and a dresser had been practically torn apart in some kind of frenzied search; even the face of the mantelpiece clock had been pried open and examined. As in the other axman cases, however, no fingerprints were found anywhere, and any footprints in the yard had unfortunately been trampled by the curious crowd of neighbors that had gathered at the scene after hearing Hazel Johnson''s screams. The discovery of two axes on the premises--one bloody and obviously the murder weapon, another covered with fresh mud--led Leson to believe that two men might have been responsible for this attack.

Perhaps one had stood on the chair in the alley to keep an eye on the victims--and simultaneously on the street--while his partner worked on the back-door panel to gain entrance. This two-perpetrator idea could even illuminate one nagging aspect of the earlier attacks. Having an accomplice could explain how the axman was so successful at eluding detection, even while chiseling away at a back door--an activity that must have been noisy enough to be heard by anyone lying awake in bed or passing on the street. In other words, the axman may not have had wings (as the impressionable Bruno girl had speculated), but he could have had a second set of eyes--keeping a lookout while he performed his grim duties inside. But Leson and Marrero were not interested in solving the earlier crimes; they were concerned only with the one in their own jurisdiction, and they pursued their investigation with an aggressive single-mindedness that they would later come to regret. While interviewing the Cortimiglias'' neighbors, they gleaned hints that the Jordanos might not be the Good Samaritans they at first had seemed. According to the neighbors, the two families had been feuding for some time, ever since the Cortimiglias had taken over the languishing Jordano grocery in 1916 and turned it into a success. The Jordanos had taken back the business just a few months ago, forcing the Cortimiglias to find a shop elsewhere in Gretna.

But recently the Cortimiglias had come back, setting up a brand-new grocery on the lot adjoining that of the Jordano store. And now, just two weeks later, the Cortimiglias were lying near death after being brutally attacked in the night. When asked about the situation, the Jordanos insisted that they had made peace with the Cortimiglias and were now good friends, but Marrero had his doubts. Back on the other side of the river, Superintendent Mooney continued to insist that all of the ax attacks (except, perhaps, for the Harriet Lowe murder) had been committed by a "degenerate madman," and that "he ransacked the places he enters to create the impression that robbery is his motive." The superintendent''s desk was now covered with maps, police reports, and photos of all of the ax cases in the city, and he was reportedly poring over them night and day. According to the Times-Picayune, his collection also included "the opinions of some of the South''s best recognized scientists, placing the axman in the same class as Catherine de'' Medici, the French author Sade, and other historic degenerates." But the Gretna authorities had a far more mundane perpetrator in mind for the Cortimiglia attack. So sure were they of Frank Jordano''s guilt that they kept asking the Cortimiglias again and again whether he was the man who assaulted them.

The victims were still barely coherent and could do little more than nod or whisper in reply. But while Charles Cortimiglia (by some accounts) continued to insist that he did not recognize his assailant, his twenty-one-year-old, highly traumatized wife apparently indicated an affirmative to the question. This was enough for Chief Leson. He promptly had the younger Jordano arrested, despite the fact that the Cortimiglias'' doctor refused to "vouch for the condition of their minds." "Both Charlie Cortimiglia and his wife, Rosie, told me that Frank Jordano had committed the crime," Leson told a skeptical press. "We have worked up a strong case against him and I am satisfied that the circumstances surrounding the case justified the arrest." Frank Mooney ignored these developments in Gretna, preferring to pursue his own theory of the murders. In a high-profile presentation to the press--including, as a visual aid, a large city map marked with no fewer than sixteen alleged axman incidents--the superintendent outlined what he was now calling his "panel theory.

" There were common elements, he claimed, not just in the various ax assaults, but also in the numerous attempted ax break-ins that had been reported throughout the city over the past year. And these common elements convinced him that the crimes were all the work of a single man. The Times-Picayune reprinted the commonalities in full: Location -- In nearly all of the cases a corner house with a high board fence at the side and rear has been selected, and in most instances it was a grocery or barroom or a combination of both. Time --The hour generally has been about 3 AM. Method --Entrance has been effected by removing a lower panel of a rear door. The plan of work in each instance has been remarkably similar. Weapon --Where the crimes proceeded to the attack, an ax has been used (except in one case where a hatchet was wielded)--sometimes an ax found on the premises, sometimes brought by the murderer, but always an old ax and always left behind. The attack --Always on sleeping victims with no apparent choice between men and women, and use of the blade of the weapon as a rule.

Precautions --Complete failure to find fingerprints, together with the fact a pair of rubber gloves was left behind in one case, leads to the belief that the murderer uses rubber gloves to protect himself against identification by the fingerprint method. Robbery as a Camouflage --In practically every ax murder, while bureaus, safes, and cabinets have been ransacked, little was stolen, and money and valuables in plain sight were left behind. And in numerous instances of "panel burglaries," the work of the intruder has been so incomplete as to leave strong doubt whether robbery was the real motive. Mooney did acknowledge that each assault and break-in could conceivably be a separate, unrelated incident. He also admitted that they all might be part of a systematic campaign of revenge or terrorism by the Mafia or Black Hand. But he remained convinced that the culprit in all or most of the incidents was a "solo maniac"--"a diabolical, bloodthirsty fiend, cunning and shrewd," as the Times-Picayune described him, "a slinking agent of the devil at 3 AM." Then, on Sunday, March 16, the city received a kind of confirmation of this macabre description. The Times-Picayune reprinted a remarkable document the paper had received in the mail o.