Video of the incident showed that the gunman, who has been identified as 25-year-old Ruslan Zinin, fired at least one shot inside the draft office where men are being enrolled for Vladimir Putin’s military mobilisation order.
The draft office head was in hospital in a critical condition after being shot, said the local governor of the Irkutsk region Igor Kobzev.
“There was an emergency in the area today. In Ust-Ilimsk, a young man fired at the military registration and enlistment office,” Mr Kobzev said on Monday.
“Military commissioner Alexander Vladimirovich Eliseev is in intensive care, in critical condition. The doctors are fighting for his life. I really hope that the doctors will do everything possible for Alexander Vladimirovich to survive,” the governor’s Telegram message read.
He added that the perpetrator of the attack “will absolutely be punished”.
This comes at a time multiple draft offices have come under attack from civilians protesting the forced military enrolment after Mr Putin’s partial mobilisation order issued on Wednesday last week.
The regional governor said he has issued instructions to strengthen security measures in the area and asked everyone to “remain calm”.
Military mobilisation orders by Mr Putin have sparked heated protests in southern Russia’s Dagestan and Yakutia – which have previously contributed disproportionate numbers of soldiers in the Russian invasion of Ukraine – and at least 100 people were detained in an anti-war demonstration on Sunday.
Several videos on social media showed civilians protesting in Russian cities with chants like “no to war”, and hundreds have been arrested by the police.
At least 100 people were detained in the regional capital Makhachkala, said the independent OVD-Info protest monitoring group.
A video showed a group of women chasing away a police officer, while others showed violent confrontations between the protesters and police.
Protesters have been particularly concerned by seemingly glaring mistakes made by the Russian authorities in selecting who gets drafted for the war effort.
Incidents include students, sick people and the elderly being called up, according to local media. In one particularly mystifying example, recruiters ordered a 63-year-old diabetic ex-military staffer suffering ill health and cerebral issues to report to a training camp, according to AFP citing Russia’s state news agency RIA Novosti.
The 63-year-old from Russia’s southwestern region’s Volgograd eventuall returned home on Friday night after the error became apparent.
Another man, a 58-year-old school director Alexander Faltin, was asked to report for duty despite not having any military experience.
When Mr Putin announced the partial mobilisation, he said only Russia’s military reserves would be called upon, as well as those with past military service and other directly relevant experience.
Mr Faltin was also eventually sent home after his documents were reviewed, the report added.
Senior Russian politician Valentine Matviyenko asked all local governors in the country to avoid any further mistakes – a rare admission that some had been made.
The upper house speaker is monitoring the mobilisation campaigns.
"Incorrect cases of mobilisation... are provoking fierce reactions in society, and rightly so," she said in a statement on Telegram.
"Some are assuming that handing in their report (to their superiors) quickly is more important than correctly fulfilling this important mission," she added.
The top official said: "This is unacceptable... Make sure that partial mobilisation is carried out in full and complete compliance with the criteria. And without a single mistake!"