McKINNEY, Texas -- Nicky Sualua can only wonder went wrong.

Dallas Cowboys star Mark Tuinei's final hours were spent looking for heroin and, later, slowly dying in his antique roadster while Sualua slept beside him.

That account, revealed in a police affidavit yesterday, came from the Cowboys' running back, who was with Tuinei in the hours leading up to the former All-Pro lineman's death last week.

Police said they expected toxicology results today which could provide further evidence as to what caused the 39-year-old Tuinei to die.

According to Sualua's account, Tuinei told his friend he took the stimulant Ecstacy. The two later went to a north Dallas apartment to obtain heroin, and Tuinei went into a bedroom, "and he said 'Here it is,' '' the police affidavit said.

Tuinei emerged unsteady, "as if he was passing out," and eventually stopped breathing, Sualua said.

Sualua added that he performed CPR at the apartment until Tuinei was breathing again, but still unconscious.

Rather than seek medical help for his friend, Sualua dragged the 6-foot-5, 320-pound former player to his 1933 classic Ford roadster. Sualua drove to Tuinei's house in an affluent section of Plano, a Dallas suburb, and parked in back. "Mark was snoring loudly," the affidavit said.

Sualua got two blankets from the house and slept in the car with his friend. When he woke up, about 5:30 a.m. Thursday, Tuinei was not breathing, Sualua told police.

In a 911 tape released Friday, a man identified as "Nicky" told the dispatcher that his friend had stopped breathing. "I can't feel a pulse," he said. Tuinei was pronounced dead after arriving at a nearby hospital.

Neither Sualua, a reserve fullback for the Cowboys, nor his agent, Steve Weinberg, could be reached yesterday.

Sualua was at his suburban Carrollton home, which he purchased from Tuinei last year, but refused to answer the door. Jerry Banks, an attorney who said he is representing Sualua, refused comment as he left the house.

"He's not going to answer the door. He's not going to talk to anybody," Banks said.

Tuinei played 15 seasons for the Cowboys before retiring in 1998. He had made plans to return to Hawaii, hoping to coach high school football and teach youngsters the same skills that helped him become a three-time Super Bowl champion with the Cowboys.

Dallas police said yesterday that since Thursday, three arrests have been made at the apartment where Sualua said Tuinei went for heroin. Those arrested face various charges, ranging from heroin possession to public intoxication.

Police submitted the affidavit including Sualua's statement in order to secure a search warrant for Tuinei's home. The subsequent search yielded marijuana pipes, a marijuana cigarette, a white tablet, a cell phone and papers with phone numbers from Tuinei's house, but no heroin, according to an inventory attached to the affidavit.

Cowboys spokesman Rich Dalrymple and NFL spokesman Greg Aiello refused comment yesterday.

Aiello did note, however, that not all players are subject to random drug testing.

Players who have first-time offenses are then randomly tested, however, their names are all confidential.

Mark P Tuinei