After being arrested last week in the killings of his girlfriend and her son, Melvin McMains said he had smoked PCP shortly before the slayings, according to police.

Area law enforcement and drug-treatment officials say they weren't surprised to hear that the illegal drug may be linked to the killings.

"I wasn't at all shocked," said Lt. E. Lawrence Knutson, head of the Narcotics and Vice unit of the Howard County police department. "It's a very scary drug. It can create unpredictable results."

McMains, a 36-year-old bartender, is accused of killing Caria A. Roth, 30, and Christopher Roth, 8, early on Jan. 13. Caria Roth was shot to death and her son was stabbed many times, police said.

Christopher's 8-week-old pit bull dog also was shot dead and found next to the bodies in the living room of the North Laurel apartment.

After the slayings, McMains allegedly met police officers outside his apartment and told them, "I have sinned and killed them all."

Investigators said he again made similar statements in later interviews.

Police also said that McMains told them he was watching a television preacher that Saturday night and became convinced that Christopher was the antichrist and had to be killed.

Police said they found a small amount of PCP (phencyclidine hydrochloride) in McMains's apartment, and are treating the slayings as drug-related.

Law enforcement officials said the drug, which had its heyday in the 1960s and '70s but still flourishes in a few places around the country, has a lethal potential.

The availability of PCP in Howard County has dropped significantly since about a year ago, when police arrested Joseph Burris, alleged to be the area's major PCP distributor for more than a decade.

Burris was convicted of PCP-related charges and is serving a 10-year prison sentence.

"It used to be a very severe problem, particularly along the Route 1 corridor," Knutson said. "Now most of the PCP we see comes out of the D.C. area."

Knutson said that several violent crimes have been linked to the hallucinogenic drug in recent years.

He recalled that a female police officer made a traffic stop about six months ago and was attacked by a man who was under the influence of PCP. And, over the past few years, several accused rapists have said that they smoked the drug shortly before the assaults.

Knutson said PCP can lead to other bizarre behavior. He said a man using PCP leaped from the back of a pick-up truck into the path of an oncoming tractor-trailer. The man, who was killed, had told fellow passengers that he thought he could stop the tractor-trailer.

Drug treatment officials said a feeling of power often overcomes PCP users.

"They become kind of like in a stupor or they hallucinate," said Thomas Taylor, director of treatment at Oakview Treatment Center in Ellicott City, "and often it gives them a feeling of power or anxiety."

Taylor said that Oakview treats at least three PCP addicts a month. They tend to be blue-collar workers who use the drug after work, the same way some people pop a can of beer, Taylor said.

He said that one of the drug's dangers is that it can have wildly inconsistent effects on a user.

"You can take it one time and feel very powerful and feel like you can beat up the whole world," Taylor said. "And the next time, you become paranoid and your feet feel like rubber."

PCP damages brain cells and eventually renders addicts lethargic, Taylor said. "Their effect is very flat," he said. "They're non-emotional. They appear very calm on the surface. They've done great damage to their brain chemistry."

Taylor said that PCP users, who often go years without their addiction being detected, do not respond well to treatment that emphasizes confrontation.

"You need to be gentle and loving," he said. "To get in an addict's face and try to get him to turn around will not work. You have to encourage them to begin to feel, to look at the consequences of their behavior."