From his election to the House in 1968, freshman legislator Shea engaged in activism against the Vietnam War and supported the burgeoning modern environmental movement.

While it passed the legislature and was signed into law by Governor Francis Sargent, the Supreme Court declined to hear the state's challenge to the war's constitutionality in Massachusetts v. Laird.

[1][2] His father, the son of National Football League treasurer Dennis J. Shea, was a civil engineer and member of the faculty at the Massachusetts Institute of Technology.

[2][1] In June 1967, Shea married the former Anita Vesta McDonald, an instructor of biology at Salem State College, at Saint Mary's Catholic Church in Plainfield, New Jersey.

[10] In a race for two spots from Ward 7, he ran on a progressive platform that included providing public records of board attendance and activities.

[15] In November 1965, he ran again, this time for the Ward 7 seat being vacated by incumbent William Carmen, and initially came in 8 votes behind Boston University professor Harry H.

[20] He compiled a liberal voting record, earning himself a 100% rating – the highest of anyone on the Board of Aldermen – from the Massachusetts chapter of Americans for Democratic Action.

He surprised poll watchers by ending up the top Democratic vote-getter in the district, receiving 277 more votes than Bradley's seatmate, Paul F. Malloy.

Upon returning to their residence on Princess Road in West Newton at approximately 12:30 the following morning, Shea went to an upstairs room he used as an office and closed the door.