The man authorities said shot and killed 50 people inside an Orlando gay nightclub Sunday pledged allegiance to ISIS and referenced the Tsarnaev brothers during his shooting rampage, the Massachusetts State Police said.

"During a conference call with federal law enforcement officials a short time ago, Massachusetts State Police and other local law enforcement authorities learned that the Orlando nightclub gunman, during his rampage, pledged allegiance to ISIS and referenced the Tsarnaev brothers, the terrorists who exploded bombs at the 2013 Boston Marathon," State Police said in a statement.

The State Police said they continue to work with federal authorities who are investigating the "terrorist act."

"As previously stated, the names of the gunman and his wife did not appear in any databases of potential terrorist suspects maintained by local authorities; however, law enforcement agencies in Massachusetts continue to work with federal authorities to learn more about the nature of the statement about the Tsarnaev brothers attributed to the Orlando terrorist," State Police said.

Dzhokhar Tsarnaev, who was sentenced to death in the Boston Marathon bombings, and his brother, Tamerlan Tsarnaev, killed three people and injured hundreds after they set off bombs at the Boston Marathon finish line in 2013.

The brothers are also accused of killing MIT police officer Sean Collier and other crimes in the days after the Marathon attacks. Tamerlan Tsarnaev was killed while police chased the brothers.

Authorities have identified the Orlando nightclub shooter as Omar Mateen, a Florida man.