A man shot a Russian military officer at a recruitment office in the city of Ust-Ilimsk on Monday.
Ust-Ilimsk is located in the sparsely populated Irkutsk region of southern Siberia.
Suspect angered by call-up of reservists
Investigators said the suspect was 25 years old. According to local media reports, the suspect walked into the office saying "no-one will go to fight" and "we will all go home now."
Last week, Russian President Vladimir Putin announced a "partial" mobilization for the war in Ukraine following Kyiv's counteroffensive in the northeastern region of Kharkiv. The call-up of reservists has stirred anger in parts of the population.
A woman who identified herself as the man's mother said he was "very upset" after his friend, who had no prior military experience, received mobilization orders.
"They said that there would be partial mobilization, but it turns out that they are taking everyone," local media cited the woman as saying.
Multiple reports have documented how people with no military experience have been called to enlistment office.
Defense Minister Sergei Shoigu had earlier claimed that only Russians with special military skills or combat experience would receive call-up papers. Kremlin spokesperson Dmitry Peskov said that some papers had been sent out in error and that this was being corrected by regional authorities and the defense ministry.
Irkutsk Regional Governor Igor Kobzev said the draft office head was hospitalized and in critical condition. He added that the detained shooter "will absolutely be punished."
"I'm ashamed that this is happening at a time when, on the contrary, we should be united. We must not fight with each other, but against real threats," Kobzev said.
Protests and attacks on recruitment offices
The shooting follows scattered arson attacks on recruitment offices and demonstrations against the draft.
Two thousand anti-mobilization protesters have been detained across the country.
Protests against mobilization took place over the weekend in the Russian autonomous republics of Dagestan and Yakutia. Predominantly inhabited by minority groups, the republics have supplied disproportionate numbers of soldiers for the war in Ukraine.
The ethnically diverse Muslim-majority Dagestan region of the northern Caucasus has seen more men killed in Ukraine than any other part of the Russian Federation, according to a tally of death notices made by Russian media.
Critics have accused Russia's government of conscripting men in remote regions and in areas inhabited by ethnic minorities to avoid sparking dissent in the country's urban centers.
Thousands of military-age men have left Russia since the announcement. Kremlin spokesperson Dmitry Peskov said "no decisions have been taken" on closing Russia's borders to prevent the exodus.