Mayor Walsh and Police Commissioner William Evans today announced initiatives to try to reduce the flow of guns onto Boston streets, including free gun locks and a summit with other mayors in the area.

The offer to licensed gun owners in the city comes in a letter sent last month that also reminds them of their responsibilities to keep their guns safe - and to comply with state laws on registering the sale, loss or theft of guns.

The two point to a recent study commissioned by the city that found that nearly a third of the guns recovered from criminals and searches between 2007 and 2013 were originally purchased at a licensed Massachusetts gun dealer.

According to the study's author, Dr. Anthony Braga, of these Massachusetts-sourced firearms, almost 85 percent of them were recovered from someone other than the original, legal purchaser. Sixty-three percent of these guns had not been reported as transferred or sold to the Massachusetts Firearms Records Bureau, even though such transfers are required by law. Only 11 percent had been reported lost or stolen.

Walsh said that he is working to organize a conference of local mayors and law-enforcement officials to look at ways to stem the flow of guns into the area - many of which are purchase in other states with laxer gun laws.