How can you indiscriminately take lives like that?
It wasn't "indiscriminate". It was
VERY discriminate!
France's strict gun laws have disarmed much of its people. Thus, a single attack (ala Charlie Hebdo - pilot run?) is unlike;ly to be opposed, and police won't show up for a while. A multi-point assault will be more than local police can handle, resulting in even longer delay in the arrival of opposition.
The assault was on a Friday evening, Part 1: French people, like other free people in reasonably comfortable circumstances like to do recreational things - dine out, concerts, sports events. For terrorists, such gatherings mean lots of victims in a small area.
The assault was on a Friday evening, Part 2: For Muslims, Friday is a holy day. Thus, faithful Muslims would be unlikely to be out and about where the terrorists were going to be attacking. Any Muslims who were are just not sufficiently faithful and their deaths would be no great loss, a warning to other Muslims to be faithful.
France has a fairly large Muslim minority. At a minimum, those Muslims are camouflage among whom the terrorists can appear like ordinary, relatively peaceful (compared to the attacks), Muslims. And among that large minority are some who would be at least somewhat sympathetic. So detection beforehand would be very unlikely, and the effectiveness of the attacks would possibly be augmented.
The Qur'an teaches faithful Muslims to slaughter unbelievers if circumstances allow, and is very, ummmmmm, flexible about when doing so is appropriate. And for those killed in fighting for Allah, there's the 72 virgins. DU-folk and other spouters of the Islamophobia should read the Qur'an (in translation) some time. It should scare them @#$%less for a week or two at least!
So this multi-point assault was far from indiscriminate. In TV crime show terms, the Qur'an provides the motive, and France's laws and culture provided ample opportunity. And that last statement does suggest that it could happen here.