Jurors convicted a former New York bank executive of murder Thursday, rejecting his claim that he was temporarily insane when he stabbed his former girlfriend to death in her island bungalow.

Thomas Toolan III was automatically sentenced to life in prison without the possibility of parole for murdering New York entrepreneur Elizabeth Lochtefeld.

Prosecutors said Toolan, 39, killed Lochtefeld, 44, on Oct. 24, 2004, three days after she rejected his marriage proposal. She and the former Citigroup executive had a whirlwind romance after meeting Labor Day weekend of that year, but Lochtefeld broke it off the weekend before she was killed.

The Lochtefeld family said in a statement: "We do not rejoice that Mr. Toolan's parents have, for all purposes, lost their son, even as Beth's parents have lost their daughter. Yet we are relieved that this troubled, vengeful and dangerous man will never be able to harm another innocent person."

Prosecutors said Toolan held Lochtefeld hostage in his New York City apartment the night she broke things off, but she escaped while he was asleep and fled to Nantucket.

Toolan attempted to board a plane bound for Nantucket the day before Lochtefeld was killed, but was stopped after security screeners at New York's LaGuardia Airport found a knife in his coat. The next day, Toolan took another flight to the island, then rented a car and bought a fishing knife at a local store, authorities said.

The defense argued that Toolan was suffering from a mental disease and struggling with alcohol addiction when he stabbed Lochtefeld to death.

Defense experts claimed years of drug and alcohol abuse by Toolan had caused brain damage and left him unable to control his behavior, but a psychiatrist who testified for the prosecution said Toolan knew his actions were wrong.

Defense attorney Kevin Reddington did not return a phone call to The Associated Press. First-degree murder convictions trigger an automatic appeal in Massachusetts.