Here's a short story:

Pumwani, Kenya (CNN) -- Asha Mohamed sits in her cramped room in Pumwani slum clutching a tiny photo of her son, Harun. He's dressed in a blue-striped tie framed by a crisp white T-shirt -- a typical 15-year-old Kenyan high school student. 

But in September he vanished. "Harun woke up very early and asked his sister "what time is it?" says Asha. He kept on asking her again and again. Then, at four in the morning, he left the house." 

In her heart, Asha knew where he had gone, but the text messages later confirmed it. Harun left his school and home in Kenya to fight for al Qaeda-linked Al Shabaab. 

"It started when he was 14. He came to me many times and said "mom, I am going to Somalia to fight Jihad." I thought he was just playing." 

For years, Al Shabaab has targeted Somalis abroad to fight in their campaign to overthrown the weak transitional government. Now Kenyans, with no ethnic link to Somalia, are joining the Jihad. 

According to a recent U.N. report, there are "extensive Kenyan networks linked to Al-Shabaab, which not only recruit and raise funds for the organization, but also conduct orientation and training events." 

Many of those events centered on Pumwani, a largely Muslim slum in Nairobi. Here, residents and religious leaders speak of a charismatic young Kenyan Sheikh that arrived from Mombasa. 

They say he bravely stood up to corruption, promoted the Quran, and generously handed out scholarships to young men. And he stoked their passion for Al Shabaab.  (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: where does this story take place?
Guess: Pumwani, Kenya

Question: Are there many Al-Shabaab ties in Kenya?
Guess: Yes

Question: Is Pumwani a nice neighborhood?
Guess: No

Question: what kind of neighborhood is it?
Guess: A slum

Question: what is the dominant religion there?
Guess: Largely Muslim

Question: how old is Harun?
Guess: 15-year-old

Question: at what time did he leave?
Guess: Four in the morning

Question: what group did he join?
Guess: Al Qaeda-linked Al Shabaab.

Question: had he spoken of his plans previously?
Guess: Yes

Now answer the following question in the same format.

Question: when?

When he was 14.