MEXICO CITY (AP) _ A federal legislator and his brother were killed and his 15-year-old son was wounded Tuesday after gunmen opened fire on their car along a desolate stretch of highway near Mexico's Gulf coast.

Jose Maria Guillen, an Institutional Revolutionary Party congressman from Veracruz, and his brother Rafael were shot several times shortly after 4 a.m., in the state of Vera Cruz, Mexico's lower house of Congress announced in a statement. Guillen's son, Marco Tulio, was seriously wounded.

Investigators believe two men followed the trio as they left the legislator's home, forcing Guillen's sport utility vehicle off the road and opening fire.

There was no immediate word on a motive for the attack.

Late Tuesday, the lower house's executive committee announced it was considering a resolution that would ask federal prosecutors to aid local authorities investigating the shootings.

``I don't know if this was political but if it was, it would make the crime not only painful but repressive,'' said Eric Villanueva Mukul, head of the legislature's executive committee, said at a news conference.

Guillen was a member of the party that controlled Mexico's presidency from 1929 until President Vicente Fox took office in December 2000. He served on the lower house's Indian Affairs and Environment and Natural Resources Committees.