HARTFORD, Conn. — With the memories of the massacre at Sandy Hook Elementary School as fresh as an open wound, the Connecticut Senate passed on Wednesday what members called the nation’s most comprehensive package of gun control legislation. The House was expected to approve it later in the night.

The vote came in a deeply divided Capitol packed with angry and frustrated gun owners who arrived in buses and vans carrying signs reading “Connecticut the Un-Constitution State,” “NRA Stand and Fight” and “Shall Not Be Infringed.” And it came in a state that has historically been at the heart of the U.S. gun manufacturing industry.

But 110 days after Adam Lanza blasted his way through a locked glass door at the school and fired 154 shots in about four minutes with a Bushmaster AR-15 semiautomatic rifle, killing 20 children and six educators, senators voted 26-10 for gun, school safety and mental health legislation drawn up over the past month by a bipartisan group of legislative leaders.

Legislators called it the most divisive issue in memory and said the legislation was an imperfect response to an impossibly complex issue. Several objected to the rushed pace in which the 138 pages became available only that morning.

Donald Williams, a Democrat from Brooklyn, Conn., and the Senate president pro tempore, began discussion of the legislation by recalling the morning of the killings, on Dec. 14, when “for a few seconds, it was hard to breathe” as people took in the news. He concluded it by saying mass killings were not solely about mental health issues, as gun advocates say, but also about firearms.

“It’s access to the weapons of war, the access to the weapons that can kill mass amounts of children or adults in our schools and in our communities,” Williams said. “That’s the essential issue when it comes to mass killings.”

The Senate minority leader, John McKinney, a Republican from Fairfield who represents Newtown, where the school is, called the legislation the most important of his 14 years in the Senate and concluded by reading the names of those who died at the school.

Many were far less pleased, including gun owners and gun manufacturers who said the bill was too broad and focused on the wrong issues. They also criticized its becoming effective immediately, saying that put an impossible burden on manufacturers and retailers.

“It’s a mental health issue, not a firearms issue,” said Jake McGuigan, director of government relations for the National Shooting Sports Foundation in Newtown. “Nothing in this legislation would have stopped what happened in this horrible tragedy in Sandy Hook.”

The legislation includes a ban on the sale of magazines carrying 10 or more bullets and requires registration of existing ones.

It also includes an expansion of the existing assault weapons ban, requires background checks on all firearms sales and sets up a registry of weapons offenders.