Story highlights A letter purportedly from Adnan Rashid was made public this week

The letter blames Malala Yousafzai's actions for the attack on her

In the letter, Rashid says he was shocked by the attack

He urges her to return to Pakistan

In a letter to a Pakistani schoolgirl shot in the head on her way home from school, a senior Taliban commander purportedly tells her that she was targeted not because she advocated education for all girls, but rather for her criticism of the militant group.

The letter attributed to Adnan Rashid was released just days after 16-year-old Malala Yousafzai took the stage at the United Nations, where she delivered an emotional plea for the right to go to school on behalf of all children.

Malala was 15 when gunmen jumped on her school bus and shouted her name, scaring other girls into identifying her, in the Swat Valley on October 9, 2012. The attack sparked massive protests in Pakistan and condemnation worldwide.

"The Taliban believe you were intentionally writing against them and running a smear campaign to malign their effort to establish an Islamic system in (the) Swat Valley, and your writings were provocative," according to the letter, which was dated Monday and released to CNN by a Pakistan intelligence source.

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"You have said in your speech ... that the pen is mightier than the sword. So they attacked you for your sword not your books or school."

CNN cannot confirm the authenticity of the letter, but its validity has been generally accepted by Pakistan intelligence officials.

Rashid made headlines last year after the Taliban broke him ou t of a Bannu prison, where he was serving a life sentence following his 2003 conviction for his role in the attempted murder of former President Pervez Musharraf. Nearly 400 prisoners were freed in the jailbreak, which authorities believe was staged to get Rashid out, a former Pakistani Air Force officer.

In the letter, Rashid said he was writing -- not as a Taliban leader -- to say he was shocked by the shooting, and to express his regret that he did not warn Malala ahead of time of the attack.

The letter went on to say that the Taliban supports the education of women, as long as it adheres to Islamic law.

He urged her, according to the letter, to return to Pakistan and "use your pen for Islam and the plight of the Muslim community."

Gordon Brown, the U.N. special envoy on global education, blasted Rashid's letter.

"Nobody will believe a word the Taliban say about the right of girls like Malala to go to school until they stop burning down schools and stop massacring pupils," he said in a statement released Wednesday.

This summer in Pakistan, a teacher was gunned down in front of her son as she drove into her all-girl school. A school principal was killed and his students severely injured when a bomb was tossed onto a school playground at an all-girl school in Karachi in March.

In January, five teachers were killed near the town of Swabi in the volatile northern Khyber Pakhtunkhwa province, the United Nations says.

And, in June, a suicide bomber blew up a bus carrying 40 schoolgirls as it made its way to an all-girl campus in Quetta. Fourteen female students were killed.