Elder Joseph Israel Bookstaber, an LDS Church missionary in Thailand who died Saturday after being hit by a pickup truck, was a smart person with a bright future, his family members say.

"He was a brilliant boy," said his father, Richard Bookstaber. "He loved physics and he loved math. The thing that made him different from other smart kids is that he had a pure love for ideas and learning; he was fascinated by it."

Elder Bookstaber, 19, spent one year at Yale University, where he was a Math and Physics major. He left school last summer to serve a mission in Chiang Rai, Thailand, for The Church of Jesus Christ of Latter-day Saints.

His life came to an end after the truck struck him from behind while he was standing with his bike at an intersection. He died about 1:15 a.m. Saturday from massive head injuries at a Chiang Rai hospital, said Elder Josh Hays, an assistant to the president in the Thailand Bangkok Mission.

"He was on the way to visit a less-active member when he was hit," Elder Hays said. "He was going to remind the member to go to church on Sunday, and then he was going home."

Elder Bookstaber, Short Hills, N.J., was waiting in the right turn lane at a traffic light just after dark, about 8:30 p.m. A dark-colored pickup truck apparently swerved into the lane, struck Elder Bookstaber, swerved out of the lane and sped away. The truck missed his companion, Elder Joshua L. Jones, 21, Elder Hays said.

Elder Jones, Missoula, Mont., didn't see the accident because his head was turned, Elder Hays said. One witness saw the incident but didn't get a license plate number, police told mission leaders. Investigators don't have any leads at this point.

"He (Elder Bookstaber) was doing very well here," Elder Hays said. "All the church members in Chiang Rai praised him for the his language abilities. He had an awesome desire to do the work and he was humble about his abilities."

Elder Bookstaber began his missionary service in Thailand in September, said church spokesman Don LeFevre.

Back home, family members and friends were trying to deal with the loss.

"No father wants to lose a son," Richard Bookstaber said. "He was an incredible boy. We had a great relationship and now it's gone, not just for me, but for my kids."

Elder Bookstaber's father is Jewish and his mother is a member of the LDS Church. He also leaves behind four brothers and one sister.