A suspended state trooper who allegedly made what prosecutors called “racially tinged” social media posts pleaded not guilty Thursday to assault charges that stem from a 2018 incident in which he opened fire with his patrol rifle on a man riding an ATV on a Southeast Expressway ramp in Boston.
Matthew Sheehan, who was suspended without pay following his indictment, was among 10 troopers who responded to the Exit 18 ramp in South Boston, where at least 30 people were illegally riding ATVs, dirt bikes, and mopeds.
Troopers and one Boston police officer blocked off both ends of the ramp, according to a statement of the case filed by Suffolk District Attorney Rachael Rollins’s office, hoping to corral and arrest the drivers.
Sheehan got out of his cruiser and tried to arrest one of the drivers, but Sheehan said the suspect moved “like a cat” and escaped, prosecutors said.
In what he allegedly described as a “show of force,’’ Sheehan then went to the trunk of his cruiser, took out his Smith and Wesson M&P Patrol rifle, loaded a round, and positioned himself in front of his vehicle, prosecutors wrote.
Sheehan then fired twice at a man riding an ATV, striking the vehicle in the front wheel on the left side and wounding the driver in the left foot, according to prosecutors, who alleged that Sheehan told shifting accounts of what happened and why he shot at the man on the ATV.
“Sheehan first stated the ATV was coming at him at an angle. He then stated the ATV was right in front of him and coming directly at him,’’ prosecutors wrote.
Sheehan allegedly told State Police investigators he was “aiming above where the motor area was because that was where he [the driver] was sitting, so I was aiming at the person coming at me. And I double tapped, bang, bang.”
In the court papers, prosecutors drew a link between Sheehan’s decision to open fire and his prior social media postings on the website MASSCOPS, where he used the screen name of “BIG IRISH” and was a frequent poster between 2011 and 2017.
“The nature and context of the post[s] shed light on the defendant’s motive, intent and state of mind during this incident,’’ prosecutors wrote.
“Many of the posts are racially tinged, disparaging of women, promote or condone violence or excessive force, suggest ‘getting creative’ when finding ways to stop citizens and a lack of respect for people and human life.”
Prosecutors cited the following examples:
■ After reading a story about an unruly crowd throwing beer cans at police, Sheehan allegedly posted, “If you throw a bottle at me and hit me you will need 2 things (1) A real good dentist (for obvious reasons) and (2) A physical therapist AFTER you start walking again.”
■ After reading an account about a woman stealing an MBTA worker’s bag, Sheehan allegedly posted, “How about I leave a nice bag of knives for you to steal and maybe you can use one on yourself so we can all feel better about ourselves or I hope you are allergic to bees and I’ll leave a nice full bag of them so I can watch you suffer in front of me!!! D**** oxygen thief!!”
■ After reading a story about a 15-year-old boy being shot in Worcester early on a Saturday morning, Sheehan allegedly posted, “I’m guessing that early Saturday morning means after midnight. So WTF is a 15yr old BOY doing out at that hour of the morning??? Enjoy your fun filled adult life dodging bullets and being a non-productive s****** drag on society.”
Sheehan was released on personal recognizance after his arraignment Thursday in Suffolk Superior Court on charges of assault and battery with a dangerous weapon, and assault with a dangerous weapon.
A pretrial conference was set for Dec. 3.
His attorney, Robert L. Sheketoff, declined to comment.