(CNN) - What appears to be the final page in the notebook of Zainab Amin, the 7-year-old girl whose rape and murder has prompted outrage across Pakistan, is a poignant reminder of a life cut tragically short.
Dated January 4, the day on which Zainab was taken from near her home in the city of Kasur, the entry reads:
"I am a girl
"My name is Zainab
"My father's name is Amin
"I am 7 years old
"I live in Kasur"
According to officials, the attack on Zainab was the 12th reported in the same small area of Kasur, in eastern Pakistan. Eleven girls have been killed, and one girl survived an attack.
Angry protests broke out Wednesday and Thursday as locals accused the authorities in Punjab province of doing too little to protect their children.
Malik Ahmad Khan, a spokesman for the Punjab government, said Friday that investigators suspect that whoever raped and murdered Zainab was involved in the other attacks on girls, and so appears to be a serial killer.
Four people have been caught in connection with the previous 11 cases and several suspects are currently in police custody, he said, adding that their identities cannot yet be revealed.
DNA test results match in six of the cases, he said.
Zainab was taken from near her home in Kasur on January 4 while her parents were in Saudi Arabia on a pilgrimage, CNN's Pakistani affiliate Geo News reported. Her body was later found in a garbage pile near her home.
Protesters gathered again in Kasur on Friday but the demonstration remained peaceful. The authorities deployed troops in the town after earlier protests turned violent.
Rallies have also been held in Lahore. Elsewhere in Pakistan, people took to social media to voice their anger over Zainab's death.
Kasur district was previously at the center of a child sexual abuse scandal in which a gang of up to 25 men was accused of blackmailing scores of children into making sex videos between 2009 and 2014. The abuse was uncovered in 2015 and a number of suspects arrested.
The experience has scarred the local community. "For the last two years, we are living in fear, parents are scared to send their kids outside," Zainab's father, Muhammad Amin Ansari, told reporters this week.
Kasur regional police officer Muhammad Kausar Zulfiqar told CNN that the girl's body was found on a heap of garbage only 100 meters from her home in Kasur.
This is the 12th such case in the same 2-kilometer area, the regional police office confirmed. Zainab was first reported missing on January 5 by her uncle, the regional police office added.
The provincial government on Thursday removed the head of the unit that was investigating Zainab's rape and murder, replacing him with another police officer.
An autopsy has confirmed that Zainab was strangled and sodomized and suggests she was raped, the medical officer who carried out the examination, Dr Quratulain Atique, told CNN on Thursday.
There were torture marks on her face and Zainab's tongue was crushed between her teeth, she said. The report suggests that when the autopsy was performed, she may have been dead for two or three days already.
CORRECTION: This story has been revised to give the correct number of girls who have been attacked and killed in Kasur, in eastern Pakistan.
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