MARVIN Harrison's life story was once the kind of tale fathers whisper to their sons at bedtime - a local guy who worked hard and achieved impossible dreams.

Harrison started turning heads almost 20 years ago as a two-sport wonder at Roman Catholic High School.

The skinny kid from North Philly went on to Syracuse University, where he starred as a wide receiver alongside future Eagles quarterback Donovan McNabb.

Harrison has since found fame and fortune in the NFL, where he breaks receiving records seemingly at will. He even won a Super Bowl with the Indianapolis Colts in 2007. But now those close to Harrison are wondering if the quiet, widely respected star has fumbled away his Hall of Fame-caliber career with an alleged senseless act of street violence.

Philadelphia police acknowledged yesterday that Harrison, 35, is under investigation for allegedly being involved in a shooting earlier this week in his old North Philadelphia neighborhood.

The shooting occurred about 5 p.m. Tuesday up the block from a garage and car detail shop that Harrison owns at 25th and Thompson streets, police said.

Six shots were fired in all during the incident. An unidentified 32-year-old man - who had just been involved in a fistfight with Harrison - took a bullet to the hand. A 2-year-old boy suffered a cut under his eye from shards of glass that showered the area when an errant bullet exploded through a car windshield, police said.

From there, the story gets complicated.

The gunshot victim was dropped off at Lankenau Hospital in Wynnewood. Initially, the man told investigators that he had been wounded while driving on 61st Street in West Philly, police sources said.

Eventually, though, he acknowledged that he had been shot in North Philly. The man refused, however, to identify the person who wounded him.

Investigators later learned that the gunshot victim had been kicked out of Harrison's bar, Playmakers, on 28th Street near Cambridge, two weeks earlier, and had bickered with Harrison ever since, sources said.

On Wednesday, detectives visited Harrison's garage and detail shop, which he purchased in 2006 for $200,000, according to tax records.

Sources said that Harrison had a Belgian firearm, an FN5.7, in his garage. Harrison handed the high-powered weapon - which fires armor-piercing rounds - over to investigators.

He then spent about four hours at Central Detectives, accompanied by his attorney, Jerome Brown.

Neither Brown nor Harrison's agent, Tom Condon, could be reached for comment last night.

During a lengthy interview, Harrison acknowledged owning the gun and being involved in a fistfight on Tuesday, but said he had nothing to do with the shooting, sources told the Daily News.

Investigators informed him that ballistics tests confirmed that five of the six shell casings found at the shooting scene came from his gun, the sources said.

Last night, detectives were searching for another man who contacted them and claimed that he had been shot by Harrison, although that report remains unconfirmed, sources said.

Harrison, meanwhile, has not been charged with any wrong-doing.

"No one has actually come in here and said that he shot them, and we don't have any witnesses," one investigator noted.

But reports of the investigation, which quickly became national news, stunned those who knew Harrison, who maintained an impeccable image even after he became a wealthy NFL star.

"His nature was so calm. He literally never caused me any trouble at all," said Dennis Seddon, the head coach of Roman Catholic's basketball team.

Harrison was named the Catholic League Southern Division MVP while he was on Roman's basketball team during his senior year.

"He carried himself in a business-like manner even then, and he carried that over to his professional career," Seddon said.

"Knowing Marvin's character . . . it's beyond belief that he could be involved in something like this."

There wasn't much of a crowd at Playmakers, last night. Two people hovered near the bar, while another tended to a lonely pool table.

"Don't nobody believe none of this s- - -!" bellowed a bouncer who puffed on a cigarette outside the bar.

The bouncer, who didn't give his name, said Harrison is at his bar "from time to time" and "looks out for everybody."

Indeed, Harrison seemed devoted to giving back after he achieved stardom.

According to the Colts' Web site, Harrison has raised money for the March of Dimes, underprivileged children in Syracuse, N.Y., and also sponsors one Philadelphia high school student to attend Syracuse University every summer.

McNabb, his old Syracuse teammate, was being inducted to his high school hall of fame last night and wasn't available to comment, said McNabb's spokesman, Rich Burg. In a brief e-mail, NFL spokesman Greg Aiello said: "We are aware of the report and we are looking into it." *