AN UNIDENTIFIED MAN DROVE his car into a cement containment wall on the top floor of the MBTA’s five-story Alewife garage on Saturday afternoon, sending a 10,000-pound piece of concrete hurtling down toward the glass-enclosed Red Line T station below.

The cement block sent glass flying everywhere but amazingly the roof structure held and blocked the cement from falling all the way to the ground.

MBTA interim General Manager Jeffrey Gonneville described the driver’s actions as intentional. Several sources said it appears to be an attempted suicide that ended with the driver’s car hanging over the edge of the roof of the garage.

The driver and the circumstances of the incident are under investigation by the MBTA Police and the Middlesex County district attorney’s office.

Luckily, no one was seriously injured. Relatively few passengers were in the mezzanine at 1:30 in the afternoon on Saturday.

“This could have absolutely been a horrific event,” Gonneville said at a press briefing on Monday at the station.

The MBTA, which is already struggling to maintain service levels with aging trains and inadequate staffing levels, is now trying to deal with the fallout of an apparent suicide attempt.

With most suicide attempts, the collateral damage is fairly small. Last Tuesday, for example, a man jumped in front of a Red Line train at Park Street Station and miraculously survived, caught between the rails and under the carriage of the train. His rescue required a massive response by first responders and the shutdown of the Red Line at Park Street for a while, but little else.

First responders seek to rescue a man who jumped in front of a train at Park Street Station. (Photo by Bruce Mohl)

The Alewife garage incident will have a much longer impact, and end up costing the T at least $1 million, according to Gonneville.

Both the Alewife garage and T station were closed on Sunday and Monday and will remain closed at least until Wednesday. Red Line service currently ends at Davis with shuttle buses connecting passengers to and from Alewife every 10 minutes.

Gonneville said the MBTA is hoping to reopen the garage on Wednesday. The T is also working to provide a secure path between the garage and the Russell Field entrance to the subway station.

The cement retaining wall that was knocked out by a driver on the rooftop of the Alewife Garage. (Photo by Bruce Mohl)

It’s unclear when the main mezzanine level of the MBTA station will reopen. Gonneville said debris needs to be cleared, a new roof has to be installed in the damaged sections, and engineers need to evaluate the safety of the station.

Even when the garage reopens, Gonneville said, the rooftop fifth floor will remain closed.

The Alewife garage can handle 1,200 cars a day and the T station sees about 5,000 passengers a day, according to T officials.

Kathleen Marchi, president and CEO of Samaritans Inc., which operates a helpline for people feeling sad or upset and has a close connection with the MBTA, said anyone feeling suicidal, lonely, or depressed should dial 988 and noted there is also a peer-to-peer texting service for people up to 24 years old.