picture or pictures?

Giganews Newsgroups
Subject: picture or pictures?
Posted by:  noah71…@yahoo.co.jp (Hase)
Date: 4 Sep 2003

Please read the following sentences.

One week later, the school principal gave Lee Vang an award.
Reporters took his pictures and the mayor shook his hand.

In the second sentence, should *his pictures* be replaced by *his
picture*, a singular form?
Someone told me that, in a case like this, no matter how many pictures
the reporters take, it should be singular.
What do you think?
And, if possible, tell me why.