The Obama administration could enforce tighter travel measures on the Canadian border, making it easier to revoke the passports of suspected terrorists, after a shooting at Canada's Parliament Wednesday resulted in two deaths. The proposed border measures come as state and federal government leaders are on heightened alert for potential terrorist attacks after 32-year-old Michael Zehaf-Bibeau opened fire in Ottawa this week.

The debate is centered on whether some Canada border checkpoints that are unmanned should be guarded with more than just electronic sensors and alarms, according to CNBC. The government would also revoke U.S. passports of potential militants under the proposed changes. "At this time, there is no specific reporting to indicate that ongoing events in Canada pose a threat to the United States," Aaron Bowker, a spokesman for the U.S. Customs and Border Protection's Buffalo field office, said.

The United Nations recently warned government leaders about domestic militants eager to join Islamic State terrorists in Syria and Iraq and then return to their home countries to cause harm. U.N. Security Council Resolution 2178 defines foreign terrorist fighters as "individuals who travel to a state other than their states of residence or nationality for the purpose of the perpetration, planning, or preparation of, or participation in, terrorist acts or the providing or receiving of terrorist training, including in connection with armed conflict."

The U.S. has revoked passports to fight terrorism in the past, including that of Anwar al Awlaki, an American-born Islamic preacher who was a leading figure in Yemen-based al Qaeda in the Arabian Peninsula. The Soufan Group estimates there are at least 12,000 foreign terrorists in Syria from 81 countries. 

Bibeau, who was born in 1982, was a convert to Islam and had a history of drug use before he converted, according to CNN. His passport had allegedly been confiscated by Canadian authorities when they learned he planned to go fight overseas.