The House committee investigating the January 6 insurrection is expected to hear live public testimony on Tuesday from Cassidy Hutchinson, a former top aide to Mark Meadows, the last chief of staff to Donald Trump, according to a source familiar with the matter.

The committee on Monday abruptly scheduled a hearing for Tuesday, suggesting a sense of urgency to disclose what it said was “recently obtained evidence”. The committee had previously said it would not hold any more hearings until next month.

It is the sixth public hearing held by the committee after a year-long investigation into the Capitol attack. Two more hearings are expected next month.

The session is scheduled for 1pm on Capitol Hill, the committee announced. Hutchinson’s appearance before the committee was first reported by Punchbowl News and later confirmed by other outlets, including the Guardian.

Hutchinson has provided the committee with some of its most shocking revelations, including that Trump approved of his supporters chanting “Hang Mike Pence” and that several far-right members of Congress who had attempted to stop the congressional certification of Joe Biden’s victory sought pardons after the attack. The disclosures emerged during Hutchinson’s closed-door testimony to the committee, videos of which have been played during the hearings.

Tuesday’s hearing came as a surprise after Mississippi congressman Bennie Thompson, the chair, said last week that the panel would not hold another hearing until July. But the committee also made clear that the public sessions were prompting more witnesses to come forward, helping to uncover new evidence about what Thompson said was the “culmination of an attempted coup”.

In its episodic presentation, the committee has made use of recorded depositions with witnesses, blending the tapes with moving public testimony and dramatic speech-making from lawmakers and staff who led the investigation. At the end of each hearing, members of the panel have directed anyone with information to their tip line and called on those with direct knowledge of the events to come forward and testify publicly.

The committee recently obtained documentary footage from the British film-maker Alex Holder, who was embedded with Trump, his family and inner circle from before the election to after the January 6 attack. The committee is particularly interested in footage he captured involving phone calls and conversations among Trump’s children and top aides discussing election strategies on the evening of the first presidential debate on 29 September 2020, sources told the Guardian.

Holder is cooperating with the committee.

The hearings next month are expected to delve into the role of far-right and paramilitary groups organized and prepared for the January 6 attack and Trump’s abdication of leadership during the hours-long siege of the Capitol.