Thousands took to the streets in Pakistan’s capital Islamabad on Sunday to protest against the February hanging of Mumtaz Qadri, a police commando who assassinated Punjab Governor Salman Taseer in 2011. The army used teargas to control the situation as it grew increasingly tense, and the military was called in for reinforcement by evening.

Earlier in the day, 25,000 protesters gathered in Rawalpindi. Around 10,000 also breached Islamabad’s high security Red Zone, military spokesperson Asim Bajwa said. According to Dawn, the agitation was led by Sunni groups Sunni Tehreek and Tehreek-i-Labbaik Ya Rasool. Sunday marked Qadri chehlum – 40 days since someone’s death according to the Quran. The protesters demanded that Qadri be declared a martyr, and Shariah be implemented in the country.

Qadri was working as Taseer’s bodyguard when he shot him 29 times after the governor spoke against the country’s blasphemy law, a sensitive issue in the country. The country’s highest courts sentenced Qadri to death and he was executed in February. However, members of Sunni fundamentalist groups condemned the execution.