Finland's gun laws are likely to attract criticism after the Jokela rampage.
Of every 100 Finns, 56 own a gun, according to a study this year by the Geneva-based Graduate Institute of International Studies, putting the rate of firearms ownership in Finland third after the United States and Yemen.
The Government has said Finland's low crime rate meant there was little need for harsher gun regulations.
But Prime Minister Matti Vanhanen said that perception might change. "Definitely this will impact opinions about handguns." The Government would take up the issue later, he said.
The killer, who was 18, obtained a licence for a .22-calibre handgun from a shooting club last month.
European Union laws forbid the sale of weapons to those under 18 except for hunting or target shooting.
This year the EU proposed raising the legal age for all gun possession to 18 but Finland protested, saying hunting was a popular leisure activity.
The proposal allows minors to use guns only if with a parent or guardian.
Last year, national statistics said Finland's 5.3 million inhabitants included 300,000 hunters, of whom 38,000 were under the age of 20.
Anyone 15 and over can apply for a gun licence with local police if they can offer a valid reason. The easiest way to get a licence is by joining a shooting or hunting club, as the Jokela gunman did.
If under age, a Finn needs to have his or her legal guardian's approval to apply. In addition all applicants are checked for a clean criminal record and whether they have any disability that could affect their gun use.
Violent incidents are rare at Finnish schools and metal detectors, common in the United States, are unheard of.
The killings at Jokela school could change all that, said Turku University history professor Timo Myllyntaus.
"This is very brutal violence with no obvious reason and seemed to have been very carefully planned and might change the school and university life in this country. Finnish schools and universities are very peaceful compared to American ones."