The man left the bus. It was soon stopped by Kenyan police, who took Baxam into custody.
Baxam now believes the man was an informant, according to Phillips. Baxam was held at the Anti-Terrorism Police Unit in Nairobi.
In court on Monday, Baxam's attorney objected to court papers that accused Baxam of engaging in terrorist activity. Baxam is charged with attempting to provide material support and resources to al-Shabaab.
"My concern, your honor, is that this case not be blown out of proportion," attorney John Chamble told Connelly.
Connelly directed that the paperwork be corrected to reflect the charge.
The Harakat Shabaab al-Mujahidin — also known as the Mujahedeen Youth Movement and other names — was the militant wing of the Somali Council of Islamic Courts that took over most of southern Somalia in 2006.
Although it was soon routed by the Somali government and Ethiopian forces, U.S. officials say the group has continued a violent insurgency with guerrilla attacks against the Somali government, African Union peacekeepers and international aid organizations.
While most of its fighters are interested primarily in gaining an advantage in Somalia, officials say its senior leadership is affiliated with al-Qaida, and some affiliates are believed to have trained and fought in Afghanistan. The group has issued statements praising Osama bin Laden and linking Somalia to al-Qaida's global operations.
Al-Shabaab has claimed responsibility for suicide bombings targeting government officials, and officials say the group has assassinated Somali peace activists, international aid workers, civil society figures and journalists.
Baltimore Sun reporter Yvonne Wenger contributed to this article.