Cellphone data shows Shaheen Syed, 21, was in the same “general area” of Albuquerque as his father at the time of the Aug. 5 killing of 25-year-old trucking entrepreneur Naeem Hussain, according to a filing by federal prosecutors for a Monday detention hearing during which Syed was denied bail.

Syed’s attorney John Anderson said the allegations were “exceedingly thin and speculative.”

Police last week charged Shaheen Syed’s father, Muhammad Syed, 51, with two of the murders and linked the four killings to personal grudges, possibly fueled by intra-Muslim sectarian hatred. Shaheen Syed was arrested last week on federal firearms charges for providing a false address.

“Law enforcement officers also have recently discovered evidence that appears to tie the defendant, Shaheen Syed, to these killings,” the filing said.

Agents believe Shaheen Syed observed Naeem Hussain leaving an Aug. 5 funeral service for two of the murdered Muslim men, based on FBI analysis of cell tower data. He then followed Hussain to the area of a parking lot where he was shot dead.

“Telephone calls between Muhammad Atif Syed and the defendant (Shaheen Syed) would be consistent with quick surveillance calls, both before and after the shooting,” the filing said.

Prosecutors did not provide evidence on the other shootings.

Imtiaz Hussain said he believed at least two people were involved in the Aug. 1 murder of his brother Muhammad Afzaal Hussain.

A pistol and rifle were used to shoot Afzaal Hussain, a city planning director, 15 times in around 15 to 20 seconds, according to police records and Imtiaz.

“For one suspect it is difficult to use two weapons in that short an interval,” said Imtiaz Hussain.

The victims Naeem Hussain and Afzaal Hussain were not related.

Muhammad Syed, an Afghan refugee, has been charged with killing Afzaal Hussain, who was from Pakistan, and cafe manager Aftab Hussein, 41, who had ties to Afghanistan and Pakistan. A fourth man, supermarket owner Mohammad Ahmadi, 62, was shot dead on Nov. 7, 2021.

Police have said they are working with prosecutors on potential charges for the murders of Naeem Hussain and Ahmadi.