McDonnell took the brunt of the blast to his body and face. The bomb was packed with inch-long industrial fence staples, which severed his jugular vein and lodged in his brain. He would die two days later without regaining consciousness.
Investigators would later surmise that the explosion had been intended to coincide with the 11 p.m. turn of the watch, when roughly two dozen officers would be coming on or going off duty. As it was, many were still changing in the second-floor locker room. Rushing downstairs, they found Officer Frank Rath, who had been in the business office with McDonnell, stumbling dazedly around the room with his gun drawn. Blood and staples covered the floor.
"I was a Vietnam veteran. I'd been in a war," recalled retired police sergeant James Pera, then a 24-year-old patrol officer, who was one of the first on the scene in the minutes after the bombing. "But I never expected this to happen in my hometown, in a police station. It was something we never expected to see in our own country."
Awash in revolutionary and antiwar fervor, the Vietnam era was a dangerous time for cops. McDonnell was not American law enforcement's first casualty, and he would not be its last. Police continue to investigate his murder, which remains unsolved.
Information in the long-running investigation into the Park Station bombing has been closely held by authorities, who still cling to hopes of bringing charges in the nearly 40-year-old case. Yet rumors have circulated for decades that the Weather Underground, a militant leftist group, was involved in the attack.
National interest in the Weather Underground was revived last year during the presidential campaign, when Republicans and conservative bloggers tried to smear Barack Obama for his ties to the group's former leaders, Bill Ayers and Bernardine Dohrn. A married couple now comfortably ensconced in the ranks of Chicago's liberal intelligentsia, Ayers and Dohrn were early political patrons of Obama's, hosting a campaign event for the future president in 1995 when he ran for the state Senate in Illinois.
Ayers and Dohrn assert today that the group deliberately avoided killing people in a campaign of "symbolic" bombings of empty government buildings. They and other former Weathermen have dismissed as a right-wing conspiracy theory any suggestions that their organization was responsible for the Park Station bombing.
Now, speaking publicly for the first time about the investigation, former FBI agents have told Village Voice Media the basis for their belief that the Weather Underground was behind McDonnell's murder. The agents have revealed that two credible eyewitnesses — both former left-wing radicals tied to the Weathermen — gave detailed statements to investigators in the 1970s alleging that Dohrn and Howard Machtinger, another member of the group, were personally involved in organizing the deadly attack. Both witnesses claimed to have participated in meetings where the bombing was planned, and one confessed to having cased the police station for the Weathermen before the explosion.
Working from these statements, authorities have quietly devoted far more attention to the Weather Underground in recent years than was previously known. Dohrn, Machtinger, and Ayers were all targets of a secret federal grand jury investigation in 2003 into McDonnell's killing, according to San Francisco criminal defense lawyer Stuart Hanlon, who has become familiar with the Park Station case while defending a client charged in another 1970s police murder. While indictments against the three were never issued, Hanlon said, "it was clear they were the targets. They weren't called — other people were called about them. The Weather Underground was the target of Park Station [investigators]."
The case against the Weathermen is far from complete. Still, given the multiple witnesses tying the group's former members to the killing of a police officer, some investigators say they are troubled by the impunity with which Ayers and Dohrn have peddled a version of the past wiped clean of bloodshed.
"I don't think they should be besmirched. I just think the truth should come out," said retired FBI Special Agent Willie Reagan, who investigated the Weathermen in the 1970s and served on a task force that reopened the investigation into McDonnell's murder in 1999. "There's so much there. If you've ever been in a courtroom, you know defense attorneys can create doubt about anything. But common sense tells you something. Who else could it be?"
Reagan, 68, has little in common with the partisans who tried to make hay from Ayers' militant past during the 2008 election season. A gruff career undercover investigator who now lives in retirement north of San Francisco, he has deployed his talents for disguise and detection to help bring down extremist groups of all political stripes.