Washington State Patrol troopers arrested a 21-year-old Kent man on Thursday morning on an outstanding warrant for vehicular homicide and vehicular assault in connection with an Oct. 24 crash in Burien that killed a SeaTac mother and injured her son.

Troopers arrested Manoj Siwakoti at his parents’ home on the East Hill in Kent, according to a State Patrol media release. King County prosecutors had previously charged Siwakoti with vehicular homicide and assault but he failed to appear at a mandated court appearance. He is in custody in the county jail at the Maleng Regional Justice Center in Kent with bail set at $25,000. He is scheduled to be arraigned on Thursday, March 17.

Lilliam L. Portillo, 41, was killed when her 1996 Toyota Corolla was hit while driving from northbound State Route 509 to westbound State Route 518 at about 3 p.m. According to charging papers, Siwakoti, driving a 2012 Nissan Rogue, failed to stop at a red light at the intersection while traveling eastbound on SR 518 and struck Portillo’s vehicle. Portillo died at the scene. Her 10-year-old son suffered injuries to his liver, elbow and hand.

Traffic investigators estimated Siwakoti was driving about 50 mph in a 35 mph speed zone when he ran the red light and hit Portillo’s car. He was driving his father’s vehicle.

Toxicology results showed that Siwakoti was impaired by prescription drugs, according to the State Patrol.

Siwakoti told troopers at the scene that he was just following his GPS.

“I go through red light trying to make U-turn,” he said to a trooper. “I just did what GPS say.”

But troopers noted that the driver appeared to be impaired from drugs because of his poor balance and coordination and his watery eyes. Siwakoti admitted that he has a prescription for anti-anxiety medication but said he hadn’t taken any that day, according to charging papers.

The driver agreed to a full drug recognition expert (DRE) exam at the State Patrol office in Tukwila. A DRE officer contacted him at the crash scene and noted obvious impairment from a central nervous system depressant. A blood test at Highline Medical Center showed that Siwakoti had fluoxetine in his system, a drug sold as Prozac, an antidepressant that may impair thinking and reactions or activities that require alertness, such as driving.

Witnesses to the accident included Portillo’s husband, who was driving another vehicle right behind his wife. He saw his wife’s Corolla pull out into the intersection and get hit by a Nissan Rogue. Another witness also saw the collision.

Troopers arrested Siwakoti at the scene for investigation of vehicular homicide and assault. He was booked into the county jail on Oct. 24 and released on Oct. 28.