Cardinal Sean O’Malley recounted experiences from Washington, D.C., to the West Indies as he warned of the dangers of a ballot question that would legalize marijuana in the state, joining Gov. Charlie Baker, Boston Mayor Martin J. Walsh, and members of the faith community in opposition of Question 4.

“I spent two years as a prison chaplain, where I saw all of these young people whose lives had been destroyed by drugs,” O’Malley said after the press conference at the Deliverance Temple Worship Center in Dorchester. “Then as a pastor in Washington, D.C., for 20 years, virtually every funeral I had was a murder and so often it was provoked because of the drug traffic.”

O’Malley argued that marijuana is not an answer to the state’s opioid problem, calling it a gateway to stronger drugs.

“I saw how people began with marijuana and then it became marijuana and alcohol and marijuana and cocaine,” he said, adding he spent 10 years working in the West Indies seeing people addicted to ganja, “seeing how people’s brains had been fried.”

The Boston Archdiocese announced Friday it had poured $850,000 into the Campaign for a Safe and Healthy Massachusetts, which is opposing legalization. The money came from the unrestricted Central Ministry funds, not from parish collections or money designated for parish support, an archdiocese spokesman said.

O’Malley said he had not believed the initiative to legalize marijuana, which has already been passed in Colorado and Washington, would ever “get legs” in Massachusetts. He acknowledged the “Yes” vote on Question 4 is ahead in recent polls.

“I think the more the word gets out, the better chance we have at turning it around,” O’Malley said. “I am confident if we can get the word out, the people will make the right choice.”

Baker said he had concerns about where dispensaries would open and scorned the question as “6,000 words written by the marijuana industry, for the marijuana industry.”

Walsh said he started his day offering condolences to the parents of someone who had died as a result of drugs and alcohol.

“I don’t think there has ever been a question I am more opposed to than ballot Question 4,” Walsh said. “I have to make too many phone calls like I did to parents today to say ‘I am sorry about your loss, your son or daughter’s pain and suffering is over now, because they are no longer with us.’”