Who sent the letter bomb that killed Arnold Drapkin?

Arnold Drapkin

   Next time you roll by the forlorn building at the corner of William and St. Thomas just south of downtown, think of mild-mannered Arnold Drapkin, who was killed by a letter bomb at his office there 1332 Notre Dame W. on 9 a.m. on Tuesday February 19, 1980.
   Drapkin's company, known as Atlantic Vending, managed pinball machines and did sound and light for such nightclubs as 1234, Bogart, Thursdays and Oz.
   He had also gained a reputation as the go-to guy if you wanted to get a booze license for your establishment, as he had apparently cultivated many profound ties to bureaucrats within the provincial alcohol licensing department.

Drapkin with his employees

   Drapkin, 35, opened the lethal missive in the presence of associates Sydney Drapkin and Saul Zuckerman as well as client Gerard Joncas, who were injured in the explosion.
  The powerful bomb had been rigged to explode when opened and investigators likened it to several terrorist bombs they had seen in separate past incidents.
  Zuckerman was the owner of the 1234 discotheque, the hottest thing in town those days and had a small company with Drapkin called Mass Laser.
   Some accounts had it that the controversial Mike Bookalam, Zuckerman's partner in the 1234 disco, was also present but it appears he was not there.
   The four men had been talking about the weather in Acapulco and the Lake Placid Winter Olympics, according to Zuckerman, who sported an eye patch for some time after sustaining his injuries.
     Police suspected a link between the bombing and an explosion inside Arviv's disco at Yonge and Bloor in Toronto four weeks earlier. That bar, owned by Arnold Arviv, was known to be full of drug dealers. Arviv, who knew Drapkin, had been charged, alongside Toronto Outlaw boss Frank Lenti, in an attempted murder/extortion of someone named Jack Mamann.