Peter Holmes Berge, a prominent attorney accused of fatally hitting a runner while driving early Wednesday evening in St. Paul, underwent brain surgery Monday, a longtime friend said.

Doctors found four lesions in Berge’s brain and removed part of one for a biopsy, said Mike Salovich of St. Paul, who has known Berge since their days as students at St. Olaf College.

“The doctors are trying to figure out what’s wrong,” Salovich said. The lesions “are small but what they worry about is they’re the spread of cancer from some other part of his body.”

St. Paul police said last week that they suspected Berge was impaired by drugs or alcohol and on his cellphone when he crashed into Scott A. Spoo, who was running on Mississippi River Boulevard at Dayton Avenue in St. Paul about 4:40 p.m.

Spoo, 35, of Woodbury, died a short time later. He was an avid runner and bicyclist who had worked for 3M for 11 years and was an engineer in the company’s stationery and office division.

A memorial service for Spoo is scheduled for Wednesday in New Richmond, Wis.

Berge, 60, was arrested after the accident. A breath test showed no alcohol in his system, and he told officers that he hadn’t taken any drugs or medication. Police obtained a search warrant to take blood for toxicology tests. Those results could take months, authorities said.

He was released from Ramsey County jail on Friday morning pending further investigation. The first inkling that something was wrong came after that, when Berge, an avid semiprofessional guitar player, began having trouble with fine motor skills. His attorney took him to Abbott Northwestern Hospital in Minneapolis, Salovich said Monday night.

Salovich said he has “no idea” whether the brain lesions contributed to the accident. He said he is certain Berge was sober and “he does not use drugs, absolutely,” Salovich said.

When they went out, Berge always insisted on using Uber, he said. On a trip to California with friends, he volunteered to be the designated driver every day.

“Maybe in the privacy of his home he’ll have wine,” Salovich said. “But he’s very responsible, very considerate, very cognizant of the dangers of drinking and driving.”

Berge is “completely devastated” by the crash, his friend said. “Knowing Peter, if he could switch places or do anything to correct this, he would.”

“When I heard about it, I was horrified,” Salovich said. “The allegations about Peter don’t match his character at all.”

“I just want to make it clear that I was not at the accident and don’t know anything about it,” he said. “But as a friend, I know his character. It’s a tragedy.”

Berge’s wife, Debbie Sit, a prominent investment adviser and philanthropist, died a year and a half ago after a 10-year battle with cervical cancer.