A member of the April 6 Youth Movement was shot late on Wednesday by security forces during a raid in a village near Cairo, the group has said.
Security forces stormed Nahya in Kerdasa to arrest suspects and disperse protests by Islamists, cordoning off areas and using birdshot pellets and tear gas, local media reported.
Khaled El-Rashidy was shot in the head and is in a critical condition in hospital, the group said early on Thursday.
Several others were injured.
A friend who transferred El-Rashidy to hospital was arrested.
In September 2013, security forces stormed Kerdasa, on the capital's western outskirts, to reassert control of the town which Islamist supporters of ousted president Mohamed Morsi had dominated since his removal three months earlier. A police general was killed during the operation and dozens were arrested.
There had been very little security presence in the town at the time since around a dozen police officers were killed in an attack on its main police station on 14 August 2013, the day security forces stormed pro-Morsi protest camps in Cairo, killing hundreds.