The funeral has taken place of the County Armagh man whose body was discovered in his car in Newry Canal.
Mr O'Connor was buried two years after he went missing
Gareth O'Connor, 24, went missing in May 2003 on his way to a Dundalk police station in the Irish Republic as part of his bail conditions.
Detectives believe Mr O'Connor was killed by the IRA. The IRA denied this.
Police divers found his car last Saturday. A priest at his funeral asked for those with information on the so-called Disappeared to come forward.
Father Sean Dooley told mourners at St Patrick's Cathedral, Armagh, on Saturday, that the anguish continued for those families whose loved ones had been murdered by the IRA but whose bodies had not been located.
"I appeal to anybody who has any information about the Disappeared to contact their families directly or indirectly so that other bodies may be cut down from the crosses and given Christian burials," he said.
Bernie O'Connor walks behind the coffin of her son, with his partner Leona
"How can you go home to your families every night knowing the hell these families are enduring?" he asked those who thought they could help.
Mr O'Connor's blue Volkswagen Golf was discovered close to Victoria Lock near Newry last Saturday after a two-day operation involving members of the PSNI's underwater search unit.
A post mortem failed to establish the cause of death. DNA tests were needed to identify his body.
He had been last spotted on closed-circuit television pictures driving through the County Armagh village of Newtownhamilton.
Mr O'Connor, a father-of-two, had been charged with belonging to an illegal paramilitary group - the dissident republican Real IRA.
Following the Requiem Mass, Mr O'Connor's remains were buried in a family plot in St Patrick's Cemetery.