Five men were convicted and sentenced to life imprisonment in the case. Only Thomas, believed to be the triggerman in the Von Colln slaying, eluded capture.
The break in the case came unexpectedly two days ago when River Forest, Ill., Officer Edwin Rann was dispatched to investigate a report of a pickpocket in the town.
``He saw a man fitting the description in terms of his age, standing at a bus corner,'' said Sgt. Craig Rutz, of the River Forest police in an interview yesterday. ``He started to question the man.''
Rann quickly determined that the man wasn't a pickpocket, but when the name of Melvin Taylor, which he supplied along with other information, was run in Rann's patrol-car computer, his true identity was learned, said Rutz.
``Rann just happens to be one of those kind of officers who won't let go,'' said Rutz. ``He finally was able to pin it down. He admitted he was Richard Thomas, the person that Philadelphia was looking for.''
The shooting of the two park guards was the beginning of three days of violence in the city that left Von Colln dead, six officers wounded and the city under a limited state of emergency.
Thomas' capture sparked a dramatic news conference yesterday at the Police Administration Building attended by Police Commissioner Richard Neal and his top command staff.
``We're very pleased about the apprehension of Richard Thomas because of the fact that this can bring some closure to that situation,'' said Neal, who was a young sergeant working in North Philadelphia when Von Colln was killed.
But it was a grizzled detective who kept reporters riveted as he recalled the scene at the guardhouse at 63d and Catharine Streets when he arrived to find Von Colln dead and Officer James Harrington badly wounded.
``We found Officer Harrington was bleeding from the mouth. He was being cared for by two or three different officers,'' said Robert Shelkin, who was a Park Guard detective at the time.
But it was down the hill in a wooded hollow that the sweltering Saturday evening's worst violence would be found. An officer dispatched to check on Von Colln looked inside the guardhouse and saw the sergeant sprawled dead on the floor, said Shelkin, who is now assigned to the North Central Detective Division.
According to yellowed press clippings from the time, Von Colln was shot five times as he sat at his desk. The area outside was later found to be booby-trapped with hand grenades connected to trip wires.
During the murder trial of one of the suspects, the late Judge James T. McDermott said that Von Colln's death was without ``reason or motive.''
``Von Colln was almost like a human sacrifice. They took his life away because he was there. They took it away not only because he was a man, but because he was a policeman,'' McDermott told a jury.
Six men were charged in the slaying of Von Colln and shooting of Harrington. Five were convicted of first-degree murder. Charges against one man were dropped.
Harrington recovered somewhat from his wounds, but left the force on disability. Reached at his home last night, Harrington said he planned to call Rann and congratulate him.
``I still can't get over this officer,'' said Harrington. ``This guy went beyond what he had to do.''
Neal said Thomas would be brought back to Philadelphia to face murder charges. ``If he agrees to it [extradition], we are going to bring him back as soon as possible,'' he said.
In 1980, according to Sgt. Rutz in River Forest, Thomas was arrested there under a name similar to Melvin Taylor for a ``minor traffic offense'' but was freed before an FBI fingerprint check revealed his true identity.
``They fingerprinted him, he paid a fine, he was let go,'' said Rutz. ``The fingerprints were sent to the FBI, and the FBI said, `This is the guy,' but they couldn't find him.''
On Thursday, when Thomas was stopped as he waited for a bus, the information Rann put into his computer was enough for it to spit out that he had a suspected cop-killer. ``He provided a date of birth and a Social Security number. They were close enough to other information that had been put into the national computer,'' said Rutz.
During interviews at the police station after his arrest, Thomas told Rann that he had hidden in Harlem for about 10 years after the slaying, said Rutz.
Outside of Philadelphia Homicide Division detectives, one of the first people to learn of Thomas' arrest was Officer Kurt Von Colln, 45, a 21-year city police veteran who works in the police-evidence room at City Hall.
Time has not lessened the memory of his father, nor has it softened thoughts of the way he died, said Von Colln, who was 19 when the shooting occurred.
He said Dempsey's news brought mixed emotions of relief, anger and joy.
``I don't think I will ever get over it,'' he said. ``He was my best friend. To have a parent taken away from you at that age, it's devastating. He's got grandchildren and great-grandchildren he's never seen. That hurts.''
Just as he became an officer to follow in his father's footsteps, Von Colln said his son, Kurt Jr., will do the same. He is scheduled to enter the Police Academy in June.