A 60-year-old Lexington man was killed after his bike crashed with an 18-wheeler truck in Porter Square during rush hour Wednesday morning, Oct. 5, according to the Middlesex District Attorney's Office. Bernard Joseph Lavins was pronounced dead at the scene.

The incident happened around 8:08 a.m. on Massachusetts Avenue near Christopher’s restaurant, at 1920 Mass. Ave., in the direction of Harvard Square. The truck driver remained on scene.

Lavins' family declined to comment on his death.

Elizabeth Shea, a colleague of Lavins' at Ironwood Pharmaceuticals in Kendall Square, said Lavins' death hit her and others hard.

"Joe was a friend and a colleague here at Ironwood Pharmaceuticals. He was a much adored colleague, with a fantastic mind and a generous spirit. The office is a very somber place. We all knew Joe to be a very enthusiastic year-round bike commuter. He was an advocate of bike safety and a very experienced cyclist. His commitment to safe riding makes his tragic death all the more chilling," she wrote in a written statement.

Both sides of Mass. Ave. near the crash were closed for most of the day as investigators reconstructed the crash, according to Jeremy Warnick, communications director for the Cambridge Police Department. The area opened up around 4 p.m., in time for the evening commute.

A small group of Cambridge students witnessed the crash, according to an announcement on the Cambridge Public Schools website.

"No students were involved in the crash except as witnesses. Grief counselors are being put in place at the schools students were traveling to when the crash occurred," read the statement. "If your child witnessed or becomes troubled by this incident, please contact the school if you would like assistance accessing help for your student."

This was the second crash in one week in Cambridge between a cyclist and a truck, and the second cyclist fatality this year. A 47-year-old cyclist sustained non-life-threatening injuries after crashing with a tow truck in Kendall Square on Oct. 3.

The first fatality this year happened in June when Amanda Phillips, 27, of Cambridge, was riding her bike in Inman Square and was struck by an open door of a Jeep as the driver was getting out. She was pushed into the travel lane where she collided with a moving dump truck.

In February, a 63-year-old Cambridge psychotherapist was struck and killed crossing the street in Porter Square. Marcie Mitler, who had two sons, died from injuries sustained after being struck by a car at the intersection of Somerville Avenue and White Street.

As of Tuesday afternoon, Oct. 11, the DA's Office had not released any more information on the latest Porter Square crash.

The DA's Office, the Cambridge Police Department and the State Police Collision Analysis and Reconstruction Section are investigating.

People took to twitter in reaction to the fatality. See our Storify below.