WASHINGTON (CNN) -- The parents of the man charged in the shooting deaths of two Capitol Police officers won a delay in their testimony to a grand jury that could indict their son, their lawyers said Thursday.

Russell Weston Sr. and his wife, Arbah Jo Weston, were subpoenaed Tuesday as they were visiting their hospitalized son for the first time since the July 24 attack.

The Westons' lawyers, Steven Tabackman and Henry Asbill, would not comment on details of the two-hour sealed hearing before Chief Judge Norma Holloway Johnson.

The subpoena had ordered the parents to appear Thursday morning.

Tabackman and Asbill said their clients had cooperated fully from the start with law enforcement officials and would continue to do so.

The lawyers also told reporters the Westons, who live in Valmeyer, Illinois, will return to Washington to appear before the grand jury when requested.