MAKHACHKALA, Dagestan — Three militants broke into the home of a senior investigator in Dagestan on Sunday and shot him dead after binding his wife and son with tape in the next room, police said.

The attackers shot police Lieutenant Colonel Yunus Khulatayev three times at point-blank range in his apartment in Makhachkala and then fled, police said.

The attack was believed to be connected to the officer's work, police spokesman Vyacheslav Gasanov said.

Meanwhile, a convoy of elite police troops was attacked while traveling to a mountainous district on Saturday, and 12 were wounded in a two-hour firefight, Gasanov said.

It was unclear whether any of the attackers were wounded.

In Chechnya, three unidentified men armed with Kalashnikovs ambushed a police patrol early Sunday in Grozny and killed two officers, police spokesman Magomed Deniyev said.