Lake Mary, Fla. ? A man suspected of drowning his toddler daughter and attempting to drown his 4-year-old son killed himself Monday by swerving into the path of a tractor-trailer, authorities said. His two other children were injured in the crash.

Police believe the drowning and crash that killed Bryan Christopher Randall are the result of a dispute with his estranged wife. In a suicide letter found in the wreckage, Randall, 37, wrote he wanted to kill himself and his children because he didn’t approve of how his ex-wife was caring for them, authorities said.

“I had to take them with me,” said the letter, which was released by authorities.

The note made it plain that the wreck was “a planned event,” said Lake Mary Police Chief Richard Beary. He said the case was being investigated as a murder-suicide.

The crash happened about eight miles north of the small lake where Randall’s 2-year-old daughter Yana and 4-year-old son Regal were found Sunday morning by a fisherman.

The boy was in serious condition Monday, and an autopsy was to be conducted on his sister.

Investigators said the crash occurred after Randall, in his sport utility vehicle parked on the eastbound shoulder of Interstate 4, made a hard left turn into the path of an oncoming truck hauling cars.

Randall, who is a former Ivy League basketball star, was pronounced dead at Orlando Regional Medical Center, Beary said. Eight-year-old Bryan Jr. also was in critical condition and 6-year-old Julian was in stable condition following the crash, hospital spokesman Joe Brown said.

Police said Randall picked up all four children Friday night and was supposed to return them Sunday night to his estranged wife, Lisa, but never did.

Deputy Chief Steve Harriett of the Seminole County Sheriff's Office examines the scene where a father suspected of drowning his toddler daughter and attempting to drown his 4-year-old son died when he pulled his car in front of a tractor-trailer. Two other sons were injured in the wreck Monday in Maitland, Fla.

When the children were not returned, their mother contacted police Monday morning. She was taken to Florida Hospital Orlando, where she identified the two found in the lake.

Randall played basketball at Dartmouth, where he was named first-team all-Ivy in 1988. He was named the league’s Rookie of the Year in 1985 and he finished his collegiate career as the school’s all-time assists leader, with 488 in 98 games.